Do-Loop construct is used when we do not know how many iterations will be performed , where as when we know exact number of execution on the block of code, For-Next construct is used. To use this construct we have to use a counter.

When the loop is executing we specify the increment number by which the value should be increase. Loop checks the condition whether it is true or not , if it is true then the body of the loop get executed and the variables value gets incremented by the specified number. Again, the loop checks the incremented value with the condition, if it is true then the body will execute and again increment value by the next value. But if the condition is false then it will exit the loop.